Improbable Warriors: Mathematicians Grace Hopper and Mina Rees in World War II

June 2003 · Historically Speaking39 Improbable Warriors: Mathematicians Grace Hopperand Mina Rees in World War Il Kathleen Broome Williams Between 1943 and 1945 mathematicians Grace Murray Hopper (1906-1992) and Mina Spiegel Rees (1902-1997) each held positions from which they influenced the nation's ability to wage a modern, math-dependent war.They knew of each other duringthewarand afterward theirUves intersected frequently since they moved in the same professional circles. These improbable warriors were among the few women whose war service proved profoundly beneficial to their later careers. In 1983 Grace Hopper, then seventy-six years old, was made an admiral by special appointment ofthe president ofthe United States. In 1987 the U. S. Navynameditsnew computer center in San Diego for Hopper, and in 1996, four years after her death, it launched the U.S.S. Hopper, an Arleigh Burke-class guided missile destroyer. The recipient ofnumerous medals, awards, and honorary degrees, Grace Hopper was esteemed as a pioneer in the field of computing . Admiral Hopper never went to sea, but her computer expertise and managerial skills made her a pivotal figure in the navy's march to the computer age. Even when she retired in 1986—the oldestserving officer in the navy—Grace Hopper continued working as a consultant for Digital Equipment Corporation. She died in 1992 andwas buried with full military honors in Arlington National Cemetery. Atthe heartofall these accomplishments was Hopper's brilliance in mathematics. Had it not been for World War ?, however, she might never have left the genteel campus in New Yorkwhere she was teaching. Hopper majored in mathematics at VassarCollege . AfterearningaMasters degreein 1930 and fouryears later a Ph.D. fromYak— a rare accomplishment for women in those days—she returned to Vassar to teach. But one year after Pearl Harbor Hopper joined theWAVES—navywomen—andupon graduating from midshipmen's school her mathematical skills landed herin the navy's Computation Project at Harvard University. The rapidlyexpanding data management needs ofWorld War ? accelerated the development ofmodern digital computers, especially in Britain and the United States. One American electro-mechanical device begun before the war was the brainchild ofHoward Aiken, professorofphysics and applied mathematics at Harvard. Aiken's Mark I, built by IBM, was the first functional, large-scale, automatically sequenced, general-purpose, digital computerto be produced inAmerica. When it was completed in 1944, the MarkI was installed at Harvard andwas immediately leased for the duration ofthe war by the U.S. Navy, desperate for gunnery and ballistics calculations. Aiken, a naval reserve officer, was given command of the navy's Harvard Computation Project. Aiken's computingmachine was in many ways unique. Itwas fifty feetlong, eight feet tall, and eight feet deep, filling an entire room. It had more than 750,000 parts, used 530 miles ofwire, and weighed about five tons. Most impressive were its speed and its automatic functioning. When programmed instructions were fed into the machine on punched paper tape it performed a series of arithmetic operations without human intervention . Aiken estimated that the Mark I was nearly one hundred times more productive than a manuallyoperated calculator. The original wartime staffof the Computation Labwas small—fewer than a dozen. Initially, Hopperwas one ofonlythreemathematicians writing programs for the Mark I and thus was one ofthe first-ever computer programmers. Throughoutthewarthis team, which grewto almostfortybyJanuary 1946, ran the Mark I around the clock, churning out essential data for all sorts of ordnance projects. Hopper's first task at the lab was to write a program for computing rocket trajectories. Her program accommodated inputvariables includingtargetbearing, elevation andrange, the ship's angle ofpitch and roll, drift angle, and time offlight. Until the Mark I became operational, the navy had to rely on what Hopper called "acres of girls down at Aberdeen [Proving Ground] using handdriven calculators" to create such firing tables,' and they could not keep up with the wartime demand. Anotherproblem Hopper tackled was to discern the best way for a minesweeperto locate magnetic mines. Further , she wrote a 561-page Manualthat gave a full and detailed description ofthe MarkI: all its parts and all its circuits, as well as how to programit. Years later,whenshewas asked how she learned to program the Mark I, Hopper's...